Patent Document 1 may be cited as a conventional mechanism for opening and closing two or more passages by controlling two or more valves using a single power source. The mechanism described in Patent Document 1 uses a gear as a power transmission mechanism, and both the gear and an output shaft are fixed. Further, Patent Document 2 may be cited as a conventional mechanism for controlling opening and closing of two or more passages asynchronously. The mechanism described in Patent Document 2 applies a preload to the output shaft alone and does not apply a preload directly to the gear.